High pressure fuel delivery systems utilize a common rail to accumulate and distribute fuel to fuel injectors at high-pressure while minimizing pressure fluctuations among the injectors. The rail functions as an accumulator to allow for precise control of high-pressure injection of fuel by an engine control unit (ECU) into the cylinders of an internal combustion engine at timing that is independent from the engine speed. Such high pressure fuel delivery systems are susceptible to leakage from the fuel line or elsewhere in the delivery system. If fuel leakage occurs, the leaking fuel can spray onto high temperature surfaces of an engine and cause a fire. To control fuel leakage when it does occur, a low pressure containment system has been used to channel leaking fuel to a containment tank or to return the leaking fuel to the fuel tank or the fuel pump. One such conventional containment system uses a double wall structure, which encloses a high pressure fuel line with an outer wall to form a low pressure passage between the inner high pressure line and the outer wall. A fuel leak that may develop in the high pressure fuel line would be contained in the low pressure passage.
Additionally, recent fuel systems have modified the accumulator of the common rail from a single tube-like structure from which fuel is supplied to multiple injections to a more modular approach in which a fuel injector body itself includes a volume that functions as an accumulator with pressures maintained as high as 23,000 psi (1600 bar). These modular components eliminate the need for a costly long external fuel rail by maintaining a highly pressurized fuel volume within the injector.